1. Field of Invention
This invention relates to inflatable balloon catheters for percutaneous introduction into the human body and, more particularly, to novel and highly effective inflatable balloon catheters that are designed to be inserted over a guide wire.
2. Description of State of the Art
Certain vascular diseases can be treated by inserting a balloon, called an intra-aortic balloon (or IAB) within the appropriate blood vessel and advancing it to an appropriate position in the vasculature. The balloon is then inflated and deflated sequentially as determined by the disease. Dual-lumen balloon catheters designed to be inserted percutaneously over a guide wire into a blood vessel, without vascular surgical procedures, are becoming the method of choice for providing this form of therapy.
The present method of percutaneous balloon catheter insertion requires first the placement of a guide wire within the blood vessel of the patient, followed by the placement of an introducer sheath/dilator over the guide wire into the blood vessel of the patient. After the sheath/dilator has been advanced into the blood vessel, the physician prepares the IAB for insertion by wrapping it outside the body. The dilator and safety guide portions are removed from the body, allowing only the sheath portion of the introducer to communicate with the interior of the blood vessel.
The wrapping means is removed from the balloon and a second guide wire inserted into the balloon from its catheter end fitting and advanced through the central lumen of the balloon until it exits through the opening of the balloon tip into the sheath. The second guide wire is then advanced an appropriate distance into the blood vessel. The balloon is now advanced along the guide wire until it reaches the location within the blood vessel that is appropriate for the therapy. Visualization of the position of the balloon is achieved, for example, by fluoroscopy using the guide wire or a radio opaque portion of the balloon. The guide wire is then removed and therapy is commenced. The central lumen through which the guide wire had passed is now available for blood pressure monitoring or other monitoring or therapeutic uses.
Although the foregoing procedure is a safe, rapid and efficacious way of intra-aortic balloon insertion, the prerequisite insertion of the introducer sheath/dilator is a step which requires time and equipment to perform, often under circumstances such that time is a critical factor to patient survival, as during cardiogenic shock.
The construction of state of the art introducer sheath/dilators permits the leading edge of the sheath to slip over the tapered portion of the dilator during insertion into the body tissues. This permits distortion of the leading edge of the introducer sheath. Tearing of the blood vessel may result as it is entered by the distorted portion of the sheath. Further, the balloon must be wrapped for insertion into the sheath. This is an operation which demands time and a certain degree of skill.
During the foregoing described procedure, arterial bleeding through the sheath must be carefully controlled during the time interval between the removal of the guide wire and dilator from the sheath and the insertion of the wrapped balloon. Often, especially in a hypovolemic patient, this loss of blood may be critical. Also, when the balloon is wrapped, spiral interstices are produced along its length. The interstices of the wrapped balloon membrane do not provide for the complete occlusion of the sheath. Therefore, a certain amount of arterial bleeding takes place during the time that is required to fully insert the wrapped balloon membrane portion of the balloon catheter into the blood vessel.
In some cases, the sheath may have to be withdrawn partly from the percutaneous wound to permit complete introduction of the balloon membrane into the sheath, especially in those cases of extreme vascular tortuosity. This creates an additional loss of critical time and of critical blood.
The wrapped balloon must be advanced entirely through the restrictive confines of the sheath and then through a portion of the abdominal aorta in order to reach its proper position in the patient's thoracic aorta. The physician must judge whether the resistance felt is merely the result of passage through the sheath or is actually caused by the balloon's having entered a false lumen or aneurysm of the aorta after it has emerged from the sheath.
In the present state of the art, the balloon is required to be advanced beyond the confines of the sheath after some portion of its passage into the aorta. In the case of an extremely tortuous or diseased arterial system, the balloon may have to leave the sheath almost immediately upon entering the arterial system to be guided only by the guide wire. During this unprotected passage through the diseased arterial system it is liable to injury or puncture by sharp calcific plaque extending from the blood vessel walls.